Raybestos was the OEM supplier for your car when built. They still make brake shoes today in Canada. AC-Delco sourced the drums but didn't actually cast or machine them (AC-Delco stopped manufacturing everything in 1962 and became a reseller only from that point on). Drums are the same for metallic or organic linings; they just wear out faster with an aggressive shoe.
You can install a wider Police/Station Wagon drum on your car for better stopping power; but you have to have the matching backing plate to match the wider shoe. Backing plates are not reproduced so you need to find a matching year Station Wagon or a an old cop car (it has to be a cop car not a passenger car with black and white paint) for the backing plate in a junk yard or on-line. You can tell a cop car by the HD suspension parts and a speedo that says "certified".
Most corner auto parts stores buy their brake parts from India or Pakistan. They are of lower quality than their usual Chinese imports. I would go to NAPA and buy the "Premium", aka high priced spread) to get a made in Mexico or Canadian part that won't kill you or others on the road.
Hi.... Anyone have a part number/brand for rear metallic shoes and compatible drums for the rear on a 66?
All rear shoes for your 66 (actually 65-70) full size Chevy were 11" X 2", regardless of the application. The industry number for the shoes was 228. However I can't tell you anything more than that other than to try as Jason suggested shopping parts stores using that number.
Wagner's rear brake drum number in my 1985 parts book was BD60001.